Integrated pest management (IPM) is a crucial approach for structural pest control operations. This approach is especially important for managing rodents and involves the following steps:
While implementing any one of steps 2, 3 or 4 alone may achieve some degree of rodent control, rodent pest management is most effective and efficient on a long-term basis when all of these steps are integrated.
Effective rodent management programs begin with quality inspections. The inspection enables PMPs to implement a program that is cost-efficient while also helping to minimize the chances of any serious mistakes or injury to non-targets, as well as to reduce the occurrences of profit-eating callbacks.
By following these steps, we can ensure that our pest control operations are effective and efficient.
To conduct a quality inspection, our professionals are alert for as many rodent signs as possible. These include fecal pellets, tracks, gnawing damage, burrows, runways, grease marks, urine stains, live or dead rodents, rodent sounds, and rodent odors (especially mice)
Fecal pellets (“droppings”) are the most commonly encountered signs of a rodent infestation. While rodents are active, they are regularly defecating. The house mouse may produce between 30 and 100 fecal pellets daily, while rats may excrete 30 to 50 fecal pellets daily. Mouse fecal pellets measure from 1/8 to 1/4 in. long with at least one - and sometimes both - ends pointed. The fecal pellets of the Norway rat measure-1/2 to 1 in. in length, and usually at least one end is blunt.
Rodent feces are usually shiny black or brown, but the color may vary depending on age and what the rodent has been eating. Feces that are very fresh are usually soft. Mouse feces become hard and brittle in most environments as soon as three hours. Rat feces may remain soft for up to 24 hours depending on the environment.
Active infestations and the high-activity areas of the rodents can be determined by removing old fecal pellets and noting the presence and locations of any new feces.
While inspecting for rodents, we don't confuse the feces of rats or mice with the feces of other animals that may also be active in the building or area, such as American cockroaches, crickets, toads, bats, squirrels, etc. Cockroach fecal pellets tend to be slightly smaller and more slender than mouse droppings and usually contain distinct ridges along the dropping. Also, American cockroach and other large insect droppings are blunt on both ends. Bat and toad droppings are made up of mostly insect fragments and disintegrate easily when pressed. In addition, the droppings of toads and insects do not have any hair fragments.
Squirrel feces appear similar to rat droppings, although squirrel feces are typically about 1 in. in length and are often twisted at the pellet’s midpoint, or two pellets are attached with a narrow pinch. Also, when attempting to differentiate squirrels from rats, a full inspection should be conducted analyzing animal sightings, locale, etc.
Because the feces of each of these animals are most often black, color cannot be used as a distinguishing feature.
Rodent tracks are easily seen where there is dust or soft moist or wet soil. The commensal rodents have five toes on their hind feet and four toes on the front feet. It is usually the hind foot that leaves the most visible track. The hind foot track of a rat will measure about 3/4 to 1 in., whereas the mouse’s hind foot track will measure only about 3/8 in. or less.
Rodents especially rats sometimes leave “tail drag” marks that will appear between their foot tracks. Sometimes a tracking patch of talc (unscented baby powder) can be placed in suspected rodent areas to verify the presence of rats or mice as well as their traveling patterns within an area.
Gnawing damage to various items or parts of buildings is commonly seen in rodent infestations.
As mentioned earlier, rodents possess a single pair of incisor teeth that grow constantly at the rate of 0.3 to 0.4mm (0.011 to 0.015 in.) each day. But contrary to popular belief, rodents do not have to gnaw on objects to keep these incisors in check. Rodents grinding each pair of incisors against one another simply keeps them filed down and razor-sharp. Nevertheless, rodents do gnaw on all types of objects.
Mice frequently gnaw small, clean-cut holes about 1½-in. in diameter. In residences, the gnawing damage of mice is often seen in kitchen cabinets where they shred paper and tear holes in the corners of food boxes and bags. In bathrooms, mice commonly gnaw on bar soap stored in cabinets.
Because of the size of rat’s incisors, gnawing damage from rats can be significant. Gnawed holes may measure up to 2 in. or more in diameter and often contain rough, torn edges. Rats commonly gnaw on wooden structural members such as door corners, joists of flooring and ceilings, wall studs, etc.
The soil burrows of rats may be found next to walls, along foundations or beneath debris or shrubbery. Generally, there are three burrow holes associated with an established brown rat family: one main hole and two bolt holes. The main entrance is usually clear of vegetation and the burrow entrance appears compacted and smooth. In some instances, fresh soil will have been recently kicked out of the burrow. The escape holes are often partially covered with leaves or other debris and will have the appearance of being “old.”
To verify active burrows, wads of paper can be stuffed into the opening or the burrows can be caved in and rechecked a day or two later.
Rats will also establish ground and wall burrows in sidewalks, curbs and brick foundation walls. To confirm whether such holes are active rat burrows versus simple deteriorating cement or brick, look for darkened smudge marks and the presence of rat hair around the hole perimeter.
Roof rat nests may be loosely constructed in woodpiles or in other locations off the ground, inside or outside of structures. They also may construct globular leaf nests within bushes, vines or within trees - especially mature palm trees containing old fronds.
Mice may also establish soil burrows around the exteriors of buildings during the warm weather months. Indoors, mouse burrows commonly occur beneath slabs. Entrance to these burrows is usually located at breaks in the slabs, between expansion joints of two slabs or around support pillar footings. Similar to rats, darkened “smudge” marks are often present around active holes.
Runways are usually evident in rodent infestations because rodents repeatedly use the same pathways between their nests and food sources. Runways are easier to detect with Norway rats than with mice or roof rats. Outdoors, fresh runways are smooth, well-packed and free of vegetation. Indoors, runways along floors or rafters usually show an absence of dust or dirt. In insulated attics, mouse runways are often evident beneath or through the insulation.
Because runways are often well marked by rodent urine, our astute professionals can identify active runways by taking a moment to smell suspected paths. Grease marks (or rub marks) from the oil and dirt of rats and mice often appear along wall areas next to runways. Grease marks may also occur around bottoms of joists where rodents have been traveling along beams or sill plates, on stairways or around burrow openings in walls, floors or ceilings. Old marks may only appear as a darkened shin (which may remain for many months until scrub-cleaned away). Fresh grease marks can be confirmed by using a thin blade spatula and scraping over the mark to note the presence or absence of “grease.”
Urine stains left by rodents may occur on their runways and in areas that they frequent. Rodent urine will fluoresce under ultraviolet (UV) light: Thus, a black-light can be used to detect rodent trails or urine contamination to items or food products. Some skill is required using black lights, however, because many items found in buildings and commercial facilities also fluoresce (e.g., food starches, rice, certain grease lubricants, some cleaning agents, etc.).
The sightings of live or dead rodents are a sure confirmation as to the presence of rodents. An inspection during the rodent’s high activity period (at dusk or just after dark) can provide information on the severity and high-activity areas.
Various sounds produced by rodents and their young, such as high-pitched squeaks, gnawing sounds, scratching, digging and sounds of rodents fighting can be heard when our professional is careful to listen and conducts the inspection quietly.
Rodent odors are usually detectable in well-established infestations, as both rats and mice produce characteristic odors from urine and various body glands.
Rodent odors may be particularly pronounced in large mouse infestations and may persist for a considerable amount of time after the mice have been eliminated from a building.
The bottom line to long-term rodent control is that rodents must have adequate food and shelter to live and thrive. Thus, wherever there is an abundance of rats or mice, there is usually also an abundance of food and shelter available. The removal or reduction of these factors alone via sanitation practices will have a very significant impact in reducing rodent populations, even without the use of any traps or rodenticides.
Good housekeeping practices are an absolute must in rodent control, whether the structure is a residence, office building or food-handling establishment. By using pesticidal rodent baits as a one-dimensional control effort without any attempt to eliminate food and shelter via sanitation, rodent populations usually rebound. Moreover, without sanitation, even the highest quality rodent baits are often not able to compete with the available foods to which the resident rodent population is accustomed.
It is difficult to entirely eliminate all food and shelter sources for mice because of their small size and the small amounts of food they require (i.e., only 3 grams daily). However, the more food and shelter easily available to the mice, the more quickly a severe infestation can result - and the more difficult it is to achieve control. Because rats require substantially more food, water and shelter than do mice, a severe infestation of rats is usually indicative of a sanitation problem. Therefore, sanitation is the backbone of a successful rat control program and will often mean the difference between success and failure in rat management campaigns.
Sanitation programs must always include both interiors and exteriors of affected buildings. Outside, all rubbish piles must be eliminated.
Improper handling of garbage and refuse (e.g., improper selection, use and maintenance of industrial dumpsters) may result in a prime source of food and shelter for rodents and thus attract them to any building. When it is necessary to accumulate food refuse, it must be kept in rodent-proof containers until it is removed from the premises. Industrial dumpsters, for example - especially those used around food-serving establishments - must be carefully selected for proper volume, placement and other factors to avoid attracting rodents to the property and allowing them to proliferate.
Grass, weeds and other undesirable vegetation adjacent to buildings should be removed, and all landscaping properly maintained. Unmanaged bushes and shrubs, ground covers (e.g., globular-shaped ornamental plantings, ground ivy, etc.) can provide rodents with both cover and food. Lumber, rock piles, rubbish, old equipment, construction materials, etc., should all be eliminated if possible. Items that must be kept should be stored at least 18 in. off the ground and 12 in. away from walls or fences.
Indoors, all potential rodent harborages must be identified and eliminated or modified. Such areas as the obscure corners beneath shelves, cabinets, worktables, lockers and equipment must not be overlooked or neglected; these dark, out-of-the-way areas are both attractive to rodents and provide them with harborage. As a minimum, keeping these areas very clean goes a long way in rodent control. Exclusion efforts in these areas as well as stairwells, machinery, double walls, false ceilings and floors, hollow tile partitions and boxed-in pipes and conduits are highly effective.
Proper storage practices are essential in rodent IPM programs. Improper storage practices often result in creating inaccessible rodent harborages.
They also prevent thorough inspections and proper baiting or trapping. Moreover, rodent damage to stored materials can be more easily detected and kept to a minimum when good storage practices are followed.
In warehouses and storage areas of commercial facilities, products should be on pallets (preferably 8 to 12 in. off the floor), 18 to 24 in. from adjacent walls, not stacked more than two pallets wide and separated by an aisle. This practice creates inspection aisles and is one of the most important rules of good housekeeping in commercial food accounts. Inspection aisles permit inspection and cleaning, reduce rodent (and insect) harborage areas, and allow for the installation of appropriate insect and rodent control measures.
Around residences, homeowners should be informed as to the importance of proper refuse management, storage practices and the proper feeding of pets and wildlife to avoid attracting rodents to the yard or home. Residential garbage cans should contain tight-fitting covers and not be overfilled. Woodpiles and any other type of outdoor storage should be elevated off the ground to eliminate rodent harborage.
Backyard infestations of rats in urban and suburban developments are commonly associated with exterior doghouses; bird and squirrel feeders; improper garbage management; improper composting practices and vegetable gardens; and improperly maintained fruit trees. In such areas, exploring rats and other pests (raccoons, skunks, squirrels, birds, etc.) will also learn to feed from spilled and surplus foods.
PMPs should educate their residential clients as to the importance of feeding dogs and cats only what they will eat and then remove the food and any spillage. Pet and wildlife foods should be stored in areas not accessible to rodents or in rodent-proof containers. Compost piles should never contain any human food scraps (e.g., meat or fish scraps).
Last but not least, fruits from trees and excess vegetables from gardens should be picked up several times each week.
Ideally, the best way to control mice and rats is to make it impossible for them to gain entry into structures. It can be difficult or impractical to exclude mice completely, as even adult mice can pass through openings 3/8 in. wide. Furthermore, mice commonly enter buildings through open doors or windows or are carried into buildings inside merchandise. Nevertheless, it is good pest management - for rodents and insects - for building owners or PMPs to rodent-proof a building as much as possible.
Every possible route of rodent access to the building must be considered. Generally, all openings greater than 1/4 in. for mice and greater-than V/2 in. for rats should be sealed. For all practical purposes, the clients can be instructed to locate any holes the size of an ordinary U.S. dime and then seal these up to deter rodents.
Points where utility lines penetrate a wall are likely access sites for rodents. The openings around service conduits such as water, electricity, air conditioning, drain pipes and vents should all be properly sealed. Sheet metal, poly-resin coated stainless steel fill fabric, hardware cloth and mortar can be used to seal the spaces around these and other types of openings.
Poly-resin coated stainless steel wool and copper mesh materials can be stuffed into gaps and holes. If only copper mesh is used, it should be mixed with mortar or the appropriate durable sealant to provide for a long-term closing of the holes. By themselves, these materials will not provide long-term rodent-proofing.
Additionally, the use of expandable foam materials that can be applied from cans is not considered effective pest-proofing materials but can provide temporary pest-proofing until a more permanent job can be completed.
Broken basement windows, warped doors and unscreened vents are all invasion routes for mice and rats. Vents should be covered with a metal grillwork, backed by rust-resistant screening. The spaces beneath doors should be checked and, if need be, reduced. A 12-in. sheet metal (26 gauge) kickplate should be attached to the outside of the door, with the lower edge not more than I/4 in. from the floor. The door casing should also be protected with sheet metal to prevent mice and rats from widening cracks by gnawing. Various anti-pest tension brushes are available on the market that provide practical rodent exclusion.
Rodents can be deterred from climbing pipes on the outside of buildings by fitting metal guards around the pipes. These should be made of 26-gauge sheet metal, fitted close to the wall at the rear and projecting 12 in. outward from the pipe. An added measure to deter climbing by Norway rats and mice is to apply a 12-in. band of hard glossy paint around the outside of brick or stone walls about 3½ ft. above the ground. A 12-in. band of glossy paint around a vertical pipe will also help prevent climbing. These measures however, may not be effective against roof rats.
Roofs should be checked to see that shingles are down tight and sheathing is complete. Also, check roof ventilators, screen vents and louvered in-wall vents. Use hardware cloth (1/4-in. width screening) to prevent larger animals from entering through vents. Screen chimneys and vent pipes if they are serving as entryways.
In the normal course of commercial pest control work, it is not always possible to do extensive rodent-proofing. And in some inner city areas that contain high populations of rodents and numerous old decrepit buildings, permanent rodent control is nearly impossible because rodents are able to get into these buildings on a regular basis. But keep in mind that there are many cases where rodent-proofing can be accomplished with a minimum of effort.
Using only a few simple tools, the professional can provide a basic rodent-proofing service as part of the control program. At the very least, PMPs should take every opportunity to educate building owners as to the importance of building maintenance and encourage them to seal holes and cracks in doors and windows and around pipes and wiring.
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